Express Scripts executed a mid-year formulary adjustment in July 2025 that moved 47 products across tiers on its National Preferred Formulary. The changes affected an estimated 24 million covered lives and triggered rebate renegotiations with at least 12 manufacturers.
The largest category affected was diabetes. ESI moved three DPP-4 inhibitors to non-preferred status while upgrading two SGLT2 inhibitors to preferred Tier 2. The shift reflects both clinical evidence favoring SGLT2 inhibitors for cardiovascular and renal outcomes, and the rebate economics of a class where manufacturers are aggressively competing for formulary position.
Mid-year formulary changes are unusual because they disrupt plan sponsor budgets and require member communications. ESI typically limits mid-cycle moves to situations where a new generic entry, biosimilar launch, or safety signal creates compelling economic or clinical justification. The scale of this adjustment suggests ESI secured significant rebate concessions that justified the administrative disruption.
For manufacturers, mid-year vulnerability is growing. PBMs historically treated formulary positions as fixed for the plan year, giving brands 12 months of predictable access. ESI's willingness to execute large mid-cycle shifts changes the competitive calculus. Brands now face year-round formulary risk, not just annual review cycles.
